Intravenous liquid infusion means for infusing patients with food, blood, drugs, and the like are used in numerous medical applications. Infusion monitors usually comprise a suitable reservoir for the solution to be infused which is connected to a dripper and from which extends a feed tube leading to an intravenous needle for injection at the venipuncture point of the patient. A tube clamp is normally placed along the feed tube to control the flow of the liquid being infused. The proper and reliable control of the rate and volume of infusing these liquids is essential to patient management and recovery. Proper infusion rates and volume may vary from a few cubic centimeters per hour to several cubic centimeters per minute. Hence, it is extremely important that the infusion rate and volume be accurately and continuously monitored and controlled.
Heretofore, the methods employed for monitoring and controlling the rate and volume of infusion have been time-consuming and of limited accuracy. Typically, an attendant sets the flow rate by counting the drops per minute from the reservoir. The rate is thus determined slowly, with difficulty and with little accuracy. Because of the heavy pressure on the attendant's time, there is usually little or no correction for any variations in the flow rate or for clearing of any blockage of the needle by clotting, etc. Such blockages can be dangerous to the patient if not readily noted and require time-consuming and painful needle replacement to re-establish flow. Similar difficulties arise when an empty bottle goes unnoticed.
In the prior art there are also provided infusion monitoring systems which monitor the amounts infused by using electro-optical sensing means. However, in such systems, the cartridge and sensing systems are quite complicated and are connected to the feeding assembly by complicated clamping means. This requires complex alignments of the optical sensing system and more complex monitoring devices.
In some prior monitors of the prior art, the optical sensing system is on both sides of the dripper tube, i.e. the emitter and the receiver are diagonally across from each other with the dripper tube therebetween. This necessitates positioning of the electrical or other controls on both sides of the tube which increases the size and weight of the monitor.
In such units, alignment of the emitter and receiver with the dripper tube properly and accurately aligned therebetween is essential in order for the optical sensing means to sense the liquid drops. Any disturbance in this alignment tends to give false readings.
Furthermore, is existing monitors, it has been noted that the tube squeezing mechanisms in use have a tendency to permanently distort the feeder tube when the tube is being squeezed so that when pressure on the feeder tube is relaxed, a permanent crimp sometimes remains in the feeder tube thus restricting the flow of fluid when such restriction is neither needed nor desired.